We can see an icon at the top-left of annotated sentences, this icon can help us to recognize if it has notes. But the icon is a little bit large, and it really have a bad impact on reading papers.

Seeking your help, plz.
https://s3.amazonaws.com/zotero.org/images/forums/u11606558/vra1dzg0xhyp3hl4mr56.png